Vectorize starting from insertelements building a vector

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189233 91177308-0d34-0410-b5e6-96231b3b80d8
Constify functions

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189234 91177308-0d34-0410-b5e6-96231b3b80d8